Heat treatment of projectiles



July 27, 1943 w. H. soDERHoLM HEAT TREATMENT 0F PROJECTILES 3sheets-sheet 1 Filed June ll, 1941 JUNCT/UN BOX JUNC770N BOX July 27,1943- w. H. soDl-:RHoLM HEAT TREATMENT OF PROJECTILES 3 Sheets-Sheet 2Filed June 11, 1941 July 27,l 1943. w. H. soDERHoLM HEAT TREATMENT OFPROJECTILES Filed June l1, 1941 pense and time;

Patented July 279 i943 l andere naar raisers/mur or rnornernns Walteriii. Soderholm, lllnited States Army, Syracuse, il.

Application .lune llllllilllll, Serial No. 397,651.

is claims. (ci. ire-ic) (Granted under the act of March 3, m83, asamended thrill 30, llf; 37@ (il. G. T57) The invention described hereinmay be manufactured and used by or for the Government for governmentalpurposes, without the payment to me of any royalty thereon.

My invention relates to the heat treatment of ordnance projectileswhereby the fragmentation of the projectile is controlled.

Previously, in the manufacture of high explosive fragmentation shells itwas necessary to produce sections of relative weakness in the shell bodyby grooving the outside or inside surfaces of the shell or by addingstrengthening rings so as to obtain a controlled fragmentation of theshell. In many cases this required additional machining operations onthe blank shell or required an elaborate casting or forging. In anyevent additional metal was required over and above that necessary toprovide a shell strong enough to withstand normal handling. Due to theirregular portions ron the outside surface, the shell would beneedlessly impeded by air resistance, or due to the presence of theirregular portions on the inside of the shell, the amount of burstingcharge which could otherwise be conned would bev diminished. in order toprovide a fragmentation shell from a blank shell it was necessary toaddadditional material, weight, ex-

there is a marked reduction in the amount of material, weight, expenseand time necessary to produce a fragmentation shell in accordance withmy invention as will clearly appear from the description of myinvention.

The fragmentation shell produced by the apparatus and method describedherein is described and claimed in my divisional application, Serial No.413,306 nled October 2, 194i.

An object of my invention is to provide apparatus for furnishing a highexplosive projectile which has strengthened portions or zonesincorporated within the body of the projectile material.

Another object of my invention is to provide apparatus for heat treatingzones or portions of the projectile material whereby subsequentfragmentation of the projectile is controlled.

Another object of my invention is to perform a. heat treatment on a highexplosive projectile so that portions on the inside surface or outsidesurface of the projectile may be strengthened.

Another object of my invention is to provide an arrangement of inductionheating coils and quenching ducts for heat treating a high explosiveprojectile whereby its fragmentation may be controlled.

Another object of my invention is to provide an -and inside of the shellarrangement whereby relative portions of the body of a high explosiveprojectile are strengthened without resorting to machining or elaborateforging operations.

Another object of my invention is to provide apparatus for furnishing afragmentation controlled projectile body at a smaller manufacturing costand with less time consumption than .those heretofore existing.

Another object of my invention is to provide apparatus for furnishing afragmentation controlled projectile shell which has a smooth outsidesurface and also a smooth inside surface so that the minimum airresistance is oered to the projectile in flight and a maximum amount ofbursting charge may be incorporated within the shell.

Another object of my invention is to provide apparatus for furnishing afragmentation controlled shell which requires no additional rings orgrooves to be formed on the cylindrical surfaces of the projectile shellto produce a controlled fragmentation.

Another object of my invention is to provide apparatus for furnishing afragmentation controlled shell of relatively light weight.

The nature and objects of my invention will be clearly revealed in thefollowing description and accompanying drawings wherein:

Fig. l represents the heating coil and quenching duct arrangementsdisposed on the outside and means for selectively controlling theenergization of `the heating coils.

Fig. 2 discloses the arrangement of strengthened portions when the otside heating coils only were energized.

Fig. 3 discloses the arrangement of strengthened portions when theinside heating coils only were energized.

Fig. i discloses the arrangement of strengthened portions when both theinside and outside heating coils were energized.

Fig. 5 discloses a view taken on line t-ii of Fig. l.

Fig. 6 discloses a modification in which noz- Zles are mounted on thespool-shaped centrally disposed spacer members.

Fig. 'l discloses a gas flame arrangement for heat treating the shell.

In this particular instance my invention is shown in relation to' anantiaircraft shell and might be applied before or after the nosing inoperation has been performed on the shell; it is understood however thatmy invention is not limited exclusively to the particular type of shell`numerals indicate like parts.

projectiles so as to control their fragmentation.

Reference ismade to the drawings wherein like The shell III is held inthe heat treatment apparatus on the base plate I1 by gravity and incentered relationship to the heat treatment Aapparatus by the circularprojection II. Magnetic induction coils I2 are equally spaced within theshell and magnetic induction coils I3 are equally spaced'surrounding theshell and on the same horizontal planes with the inner coils I 2.' Theinner coils are spaced by spool-shaped members I4. The entire innercolumn of coils I2 and spacers I4 is supported on the washer I5 which isheid against downward movement by the iixed flange I5'. The coils I2 maybe `.adjusted for height by making usel of the threaded connection I8between the tube I6 and base plate I1. 'Ihe centrally disposed tube I6has an indentation I9 on its outer surface which serves to preventrotation of the spacers I4 with respect to the tube and also to serve asa conduit for the individual coil leads 2U which might be threadedthrough a cable Each spacer I4 has a. transverse hole 2| through whichthe leads from one coil pass and also lugs 22, Fig. 5, which are adaptedto cooperate with the inside corners 23 of the centrally disposed memberI6 so as to prevent relative rotation.

A hole 24 in the base plate I1 provides an exit for the coil leads.

The upper end of tube I6 is provided with a small opening 21 so as toallow passage of the quenching iiuid which might be water or oil. Holes25 in the centrally disposed conduit I6 are arranged so that they arealigned with the holes 26 in spacers I4 thus allowing most of the`quenching iiuid to be squirted through those holes in the most effectiveregions. The holes 25, 26, 21 are graduated in size so that practicallya uniform spray is produced in the interior of the shell; the holes areenlarged more and more 'as the distance from the source of supply isincreased so as to compensate for the pressure drop of the quenching uidIf desired, nozzles 28 may be mounted overeach quenching fluid openingin thespacers as shown in the modification in Fig. 6 in order to morepositively direct the quenching liquid to the heated shell surfacealthough the addition of such nozzles is not deemed vitally necessary tocarry out my invention.

The coils I3 are spaced by the circular channel shaped members 29 whichhave circumferentially disposed'holes 40 alignedwith holes 30l in thejacket 3l. The row of coils I3 is supported on the washer-shaped member32 which is held against downward movement by a fixed bracket 33. Thejacket 3I has a recess 34 which serves as a conduit for the leads ofcoil I3; the inner edges 35 and 36 cooperate with lugs 31 and 33 on thecircular channel-shaped members 29 so as to prevent relative rotationbetween members 29 and jacket 3.

'Ihe coil mounting structures for coils I2 and I3 are preferably ofnon-metallic material and it is desirable that the shell metal itself isthe only metallic material through which the ux from coils I2 and I3 iscaused to pass.

The jacket 3| is supplied with quenching uid which passes through thetubular opening 4I.

Gate valves 42 and 43 serve to limit the now disclosed and might beapplied to other ordnance eter but some of them may be enlarged so thatY to the ones shown in Fig. 6 may be mounted in relationv to eachopening 40 so as to serve as more positive directing means for thequenching uid.

All ofthe quenching uid must pass through a magnetically operated valve44. Magnetically operated valves per se are well known in the fluiddistribution art and for that reason the particular structure of thisvalve is not disclosed. The valve is of the type in which movement ofthe magnetic member 45 upon energizaton of solenoid winding 46 opens thevalve 44 to allow a flow of iluid; upon deenergization of winding 46 thevalve 44 is biased by means not shown so as to close the valve. The coil46 is energized from a battery 41 through a single pole, double throwswitch 46 which has one set of terminals to which no wires areconnected.

The leads 2U from the inner coils pass through the opening 24 to ajunction box 49 and the leads 5I) from the outer coils which arethreaded through a cable 50 pass through the opening 5I to the junctionbox 52.

The inner or outer coils I2 or I3 may be connected in series or inparallel at the corresponding junction box or in any other manner deisired.`v When the coils I2 or I3 are connected in series with oneanother-then the net effect of the component coils I2 or I3 is to form acoil proper with each coil I2 or I3 a component of the coil proper. Thecoils might be connected with respect to one another so that the sameamount of current does not pass through each one of the coils if it isdesired to produce compensating eifects. Variable resistors 53 and 54serve to control the amount of current'fiowing to the coils I2 and I3respectively.

The double pole, double throw switch 55 serves to energize the leads 50from an alternating current source 56 through transformer T1 and leads53. Two terminals of the switch 55 are left uny 58. Two terminals of theswitch 55 are left unconnected as indicated in Fig. 1.

As a precautionary measure the double throw switches 48, 55, and' 51 maybe interlocked (not shown) so that switch 48 is prevented from beingclosed when either switch 55 or switch 51 is closed; this would preventthe shell being needlessly cooled andA heated at the same time.

It is obvious that the inner and outer coils may be individually orsimultaneously energized so that at the election of the operator innerrings of the shell material may be heated or the outer rings of theshell material may be heated or else the inner and buter rings of theshell material may be heated simultaneously. A subsequent rapid coolingof the heated parts will produce a hardening of the material winch washeated so that the shell has hardened portions as indicated in thedrawings.. Fig. 2 discloses the result obtained when the outside heatingcoils were energized; the dotted portions signify the hardened portions.Fig. 3 discloses the result obtained when the inside heating coils wereenergized and the dotted portions signify the hardened portions.

Fig. 4 discloses the result obtained when both the inside and outsidecoils were energized and producing ll. (a) Closes switch 55 or (b)switch 5l or (c) switch 55 and switch 5l, depending upon the desiredlocation of the hardened zones,

" 2. Opens all the switches which were closed in step l, and then 3.Closes switch it to cool the material.

lihc shell material is heated due to eddy currents and/or hysteresislosses in the shell material itself. is necessarily generated in thatregion through which the flux passes in accordance with wellrecognizedprinciples.

High frequency currents may be used to great advantage in producing aheated Zone near the surface of the shell material. The alternatingfluir. through the coils l2 and iii causes an alternating flux to passthrough the shell material;

The heating is local in edect and 'd the magnitude of the eddy currentsproduced in the shell material is in proportion to the freb quency ofthe alternating current and these eddy currents set up magnetic fieldsof their own which tend to decrease the distance which 'the coil nur.penetrates the shell material. The above phenomenon is commonly referredto'as eddy current shielding and is made of advantage in a heated zonenear the surface of the material. It is highly desirable that thoseportions which are to be hardened be heated above the hardeningtemperature very quickly and also quenched very quickly; otherwise theheat generated would have time in which to diiuse into the body of thematerial due to the good heat conduction of the body and instead ofhaving sharply defined hardened bands in the shell there would be ahardening of that-material which is not desired to be hardened. Theelectrical control arrangement described allows rapid operatien. Thepower supply and connected circuits should be of sufficient size andhave sufcient regulation to cause the shell material to be heated to thequenchingl temperature in the shortest possible time thus assuring aminimum, amount of heat diusion to the surrounding material.

The electrical and magnetic apparatus disclosed serves as one of themeans by which a heat treated fragmentation shell of the type describedmay be produced. IThe embodiment of my invention thus far described ismy preferred embodiment and it is understood that other means mayreadily be suggested; for instance, the portions of the shell tobehardened may be supplied by heat from a sharply dened gas flame whichis movable with respect to the shell as in Fig. 7. In Figure '7, theshell l@ is held and rotated by a lathe chuck 9U. Gas burners llt andliti supply heat to shell respectively. of the shell material will beheated above the temperature of its surrounding material. The ow of gasto the burners is controlled by the valves M2, it and duid is controlledby valve |145. The valves l `and M5 may be interlocked by means wellknown the inside and outsideof the As the shell is rotated rings Ulli.The flow of quenching in the art. The auxiliary valve it@ serves as anexit for any quenching fluid remaining in the gas pipes after thequenching operation.

It is to be understood that my invention is not limited to theproduction of a fragmentation shell of the type disclosed but myinvention in its broader aspects may be applied in the production ofordnance matriel wherein it is desired to produce different degrees ofstrength or hardness in portions of the ordnance matriel.

In general my invention may be applied in the production of handgrenades, time delay bombs, projectiles or other fragmentation body soas to control the'uniformity of the particles which are fragmented bythe bursting charge contained therein. f

I claim:

l. In the art of producing a fragmentation controlled shell, theapparatus comprising more than two spaced coaxial coils adapted topartially encase the shell, orifices disposed between adjacent coils,means to project a stream of liquid through said orifices, means formaintaining the shell stationary with respect to the coils, and meansfor spacing said coils whereby rings of the shell material are heatedwhen high frequency current is passed through the coils.

2. In the art of producing a fragmentation controlled hollow shell, theapparatus comprising more than two spaced coaxial coils adapted to bedisposed within the interior portion of the shell and in close proximitythereto, orifices disposed between adjacent coils, means for projectinga stream of liquid through said orifices, means for maintaining theshell stationary with respect to the coils, and means for spacing saidcoils whereby rings of the shell material are selectively vheated whenhigh frequency current is passed through the coils.

3. in the artof producing a fragmentation controlled shell, theapparatus comprising more than two spaced coaxial coils adapted topartially encase the shell, means foi` producing a spray of liquidwithin the cylindrical space defined by the coils, means for maintainingthe shell stationary with respect to the coils, and means for spacingsaid coils whereby rings of the shell material are selectively heatedwhen high frequency current is passed through the coils.

ll. In the art of producing a fragmentation controlled hollow shell,.the apparatus comprising more than two spaced coaxial coils adapted tobe disposed within the interior portion of the shell and in closeproximity thereto, means for producing a spray of liquid within thespace surrounding the coils, means for maintaining the shell stationarywith respect to the coils, and means for spacing said coils wherebyrings of the shell material are selectively heated when high frequencycurrent is passed through the coils.

5. In the art of producing a fragmentation controlled than two spacedcoaxial coils adapted to partially encase the shell, means formaintaining the shell stationary with respect to the coils, and meansfor spacing said coils whereby rings of the shell materialareselectively heated when high frequency current is passed through thecoils.

6. In the art of producing a fragmentation controlled hollow shell, theapparatus comprising more than two spaced coaxial coils adapted to bedisposed within the interior portion of the shell, means for maintainingthe shell stationary with respect to the coils, and means for spacingsaid coils whereby rings of the shell material are selecshell, theapparatus comprising moretively heated when high frequency currentpassed through the coils.

7. In the art of producing a fragmentation controlled hollow shell, theapparatus comprising a set of more than two spaced coaxial coils adaptedto partially'encase the shell, a set of more than two spaced coaxialcoils adapted to be disposed within the interior portion of the shelland disposed coaxially with said first mentioned set, means formaintaining the first mentioned set stationary with respect to theshell, means for maintaining the second mentioned set stationary withrespect to the shell and coaxial with the first mentioned set, means for`spacing the coils of the first mentioned set whereby rings of the outershell material are selectively heated when high frequency current ispassed through the coils yo1' the first mentioned set, and meansforspacing ,fthe coils of the second mentioned set whereby ,f rings of theinnershell material are selectively heated when high frequency currentis passed through the c oils ofthe second mentioned set.

8. In the process of yproducing a fragmentation body from a smoothsurfacedubody the steps l which comprise, heating selected portions ofthe smooth surfaced body and then quickly quenching the selected iscontrolled.

9. In the process of producing a fragmentation lbody from a hollow bodyhaving an outer smooth surface and an inner'smooth surface, the stepswhich comprise heating selected portions of both smooth surfaces, andthen quickly quenching the portions, whereby fragmentation selectedportions so as to control the fragmenta- `Ition of the body. l

10. In the process of producinga fragmenta-l` compriseheating selectedportions of the inner and outer smooth cylindrical walls, and thenquickly quenching .the selected portions, whereby fragmentation iscontrolled.

l0 11. In the process of producing a. fragmentation shell from a hollowshell having smooth cylindricalinner and outer walls, the steps whichcomprise selectively heating ring-like portions of the inner and outerwalls and then quickly l.; quenchingv the heated portions.

12. 'I'he same as claim 7 and the plane of each coil of each set iscoplanar with a corresponding coil of the other set.

13. The process of augmenting the fragmentation characteristics of ahigh explosive container formed of a ferrous metal of substantially thesame composition throughout the surface area, which comprises, heatingpredetermined areas of the container at such a rate and to such atemperature as to permit hardening of areas of controlled depth of thecontainer wall, terminating the heating when said areas attain thehardening temperature and chilling the areas so heated at such arate asto increase the hardness of the same whereby the container walls areformed of areas of relatively high and low tensile strength.

WAL'I'ER H. sODERHoLM.

Gru.

